The present invention relates to a liquid crystal display television receiver, and in particular to a liquid crystal display television receiver wherein the components are arranged such as to enable the television set to be made extremely compact, thin and light in weight, and extremely convenient to operate, and which moreover provides a clear television picture utilizing only incident ambient illumination.
In recent years, various types of portable battery-powered electronic devices such as calculators, games, etc, which are sufficiently small and lightweight to be readily accommodated within the user's pocket. Such devices generally employ a liquid crystal display, together with low-consumption circuit elements, and so have a long battery life. Various attempts have been made to produce a television receiver which will provide similar characteristics. Such prior art types of television receiver can be broadly divided into those which employ a miniature CRT and those which employ a liquid crystal display panel. It has been found possible to produce CRT type miniature television receivers which are reasonably compact, although somewhat larger in size than can be readily fitted into a pocket. However with such a receiver, the display screen is invariably small, by comparison with the outer dimensions of the set, so that the picture of a very compact receiver of this type is excessively small and therefore difficult to view. ln addition, a substantial level of power will be consumed by any type of CRT display, so that it is difficult to ensure sufficiently long battery life. Furthermore it is necessary to use very high voltages to drive the CRT, even in the case of a miniature display, and the requisite drive circuits are complex and expensive to manufacture and it is difficult to make the overall weight of the set sufficiently low. Furthermore, when a CRT type television receiver is utilized outdoors in bright sunlight, the display contrast is reduced to such an extent that it becomes difficult to view the picture.
Those compact television receivers which employ a liquid crystal display panel can be divided into two basic types, i.e. those which employ a rear-reflector type of display, in which light which is incident on the display panel passes through the panel to be reflected from a rear reflector plate to pass back through the panel towards the viewer, and those which are of transmission type, whereby the television picture is viewed as light which has passed through the display panel from a light source disposed at the opposite side of the panel. This light source can be either ambient illumination or a specifically provided light source. Either of these types of television receiver could benefit from the advantages of a liquid crystal display panel, i.e. the overall size can be made thin and compact, and the set can be made light in weight. In addition, due to the capability of operating a liquid crystal display panel at low levels of drive voltage, the drive circuits can be made very simple, and moreover the level of power consumption is extremely low. However in fact, the liquid crystal display television receiver which have been produced up until the present have been fairly large in size and excessively heavy, and cannot be said to be truly suitable for the user to carry in a pocket.
In the case of liquid crystal display television receivers which employ a rear reflector plate, there may be an insufficient level of incident illumination upon the display, since this illumination must arrive from a direction which is substantially perpendicular to the display panel, i.e. along the same direction as that from which the user is viewing the display. Thus, this incident illumination may be partially blocked by the viewer's body, chair, etc. Furthermore if the maximum level of incident illumination occurs along some other direction (e.g. from the sky, or a lamp disposed above the set), the orientation of the display screen which is most convenient for the user may be totally different from the orientation which provides a maximum level of incident light for viewing the display. Another disadvantage is that light must pass through the liquid crystal display panel twice in succession, i.e. absorption of light within the panel will occur twice, so that the efficiency of utilization of incident light is low. For these reasons, it may not be possible to obtain a sufficiently bright displayed image with such a type of liquid crystal display television receiver.
For these reasons, a liquid crystal display television receiver according to the present invention employs a transmission type of liquid crystal display panel, as described hereinafter.